4x4 rear axle in a rwd Tahoe?

[Marky Dissod]

This car is not my daily driver but more of a weekend and vacation cruiser so 3.73 should be about right.

No, 4.10 will be better. 3.73 is BARELY adequate at best.

I am also running slightly smaller diameter tires, so it will be about equivalent to a 3.80 with the stock size tire.

3.80 ain't 4.10. You've CLEALRY never driven a GM suv with a 6.0L, or a GM suv with 4.10.
Their 4L60Es last longer, and they get decent MpGs unless driven by leadfooted idjits.

It sounds like the GMT900 are a little wider so I probably don't want to mess with that.

0.5" wider on either side is not worth any concern. Open your options, don't close them.

... thanks Marky for the edit!

No thanks needed. For your sake, I hope you find 4.10 ...

 

[S33k3r]

Take a look at 2005 and 2006 Sierra Denalis. They will likely have the 4.10 gears and be AWD. That means they should have both axles you'll need. 2002, 2003, and 2004 Sierra Denalis should likely be avoided, as the rear axle will always be a Quadrasteer axle, unless someone swapped that axle out ahead of you. Also, if you have a street truck, get something with the G86. That's the limited slip differential, vs the G80 locker. Finally, make sure you check the pumpkin on anything you get. When people fail to maintain a G80, it will often grenade, taking out the axle and sometimes the truck too. I believe the Sierra Denalis came with 4.10s and G86 differentials.